Knock sensor replacement issues.

[Danzigman]

Well, I got the dreaded check engine light telling me I had a bad knock sensor. I read everything on here and other places before starting the job. I got the factory gm gaskets, harness and sensors. I used ACDelco 213-3521 sensors part number 12589867. Once I tore everything down, I found that the rear sensor was rusted. The front sensor looked new, but I replaced it any way. I found that the part number was different on the original sensor, so I searched and found that the original part number was replaced with the one I had. I cleaned out the rear hole as best I could. I reinstalled everything and made the suggested rtv C formations around the sensor holes. I did rtv the sensor plugs upon installation, other than that the only other possible issue was that my large torque wrench started at twenty foot pounds, instead of the required 15. The torque wrench i used for the intake was a 1/4 drive so I couldn't use that for the 22 socket. This being the case i installed the sensors at 20 foot pounds. The sensors were never dropped or anything. It took 149 miles before the light returned for the first time. What could be the issue? Could it be the 20 foot pounds torque? If so why is the front sensor not trowing codes?

 

[David Paul]

Watching as I'm about to replace mine......

 

[Junior_22g]

Check that video out. I watched that and its got alot of great tips for this job!

Make sure your connections are all tight on the harness. I just did this job on my 01 Yukon 5.3 a couple months ago.
I dont see the torque being the issue. I bought the correct wrench from Sears to do mine but me being me, I heard the click from the wrench and went a bit tighter. The torque specs are also there so you dont over tighten and strip or break the knock sensor.

One thing i noticed is that during cleaning out the sensor cavities, some of the rusty mess fell into part where the sensor screws in. I took a can of air and blew it out. Make sure those areas are clean too.
The last possibility is that you may have gotten a bad part. Sucks, But it's possible.

Let me know if you have any specific questions.

 

[Junior_22g]

There was mine in all it's glory. Lol

 

[Junior_22g]

And going back together.

 

[pnwdan]

i would just rtv the plugs not all over the plate

 

[bottomline2000]

Yeah, this is how i did mine and I wouldn't want to over torque the sensors..I have a sears 3/8 ratchet with a 1/2 adapter that can hit that torque figure. Goes down to 10ft lbs. Lucky they didn't strip.

Sent from my SAMSUNG-SM-G900A using Tapatalk

 

[Danzigman]

That is the video that I watched. Now I am up against the wire. My inspection is due at the end of the month. I hate to repeat the process just to have the same issue.

 

[Danzigman]

Check that video out. I watched that and its got alot of great tips for this job!

Make sure your connections are all tight on the harness. I just did this job on my 01 Yukon 5.3 a couple months ago.
I dont see the torque being the issue. I bought the correct wrench from Sears to do mine but me being me, I heard the click from the wrench and went a bit tighter. The torque specs are also there so you dont over tighten and strip or break the knock sensor.

One thing i noticed is that during cleaning out the sensor cavities, some of the rusty mess fell into part where the sensor screws in. I took a can of air and blew it out. Make sure those areas are clean too.
The last possibility is that you may have gotten a bad part. Sucks, But it's possible.

Let me know if you have any specific questions.

I watched that video as well before starting the process. Not sure what i did wrong.

 

[pnwdan]

I watched that video as well before starting the process. Not sure what i did wrong.

Did you say you put RTV in the plugs?

 

[ScottyBoy]

I just did mine last week. I have heard on another forum that it is imperative to torque the knock sensors to EXACTLY 15ft/lbs , no more and no less. If torqued more than 15, it will be overly sensitive and give you a false knock sensor trouble code. I suspect that this is what your issue is. I had to actually go out and buy two torque wrenches when I changed mine. Luckily, Harbor Freight was having a Father's day sale and had them on sale for only $10 each!
I would get a 1/2inch drive torque wrench that will read 15 ft/lbs, and pull the intake back off and redo it. You should be able to reuse the intake gasket since its new, and just redo the RTV sealant around the knock sensors.

 

[pnwdan]

Most people don't realize they can use an inch/lb torque wrench as well. 12 inches in a foot X 15 ft/lbs = 180 in/lb

 

[bottomline2000]

And don't put any dialectic grease on the sensors either. Spend the money on the right tools and save yourself the grief. Me personally, I prefer to not use a torque wrench at its highest or lowest settings..getting a 1/4" wrench to fit a 22mm socket is going to be interesting needless to say but possible.

sent from my lollipop

 

[Danzigman]

Did you say you put RTV in the plugs?

Just like bottom line did in his picture.

 

[pnwdan]

Just like bottom line did in his picture.

The giant plugs not the electrical connections though right?

 

[ScottyBoy]

The giant plugs not the electrical connections though right?

That's what I did to mine. I put blue RTV silicone on the rubber grommets that cover the sensors. Plus I made a 1/2 inch U-shaped "wall" around the rear sensor to divert any water or other fluid from settling on the rear sensor. That's what every GM service bulletin says to do when replacing the knocks sensors.
I wish I had a picture of how I sealed it, bug I do have a picture of my old knock sensors. The rear sensor was corroded as all hell, and the front one still looked basically new. There was about an inch of water in the cavity with the rear sensor that I had to suck out with a shop vac. I then blew it out with air to make SURE that it was dry before installing the new one.
I guess you can look at my picture and figure out which sensor was the rear sensor.

 

[pnwdan]

That's what I did to mine. I put blue RTV silicone on the rubber grommets that cover the sensors. Plus I made a 1/2 inch U-shaped "wall" around the rear sensor to divert any water or other fluid from settling on the rear sensor. That's what every GM service bulletin says to do when replacing the knocks sensors.
I wish I had a picture of how I sealed it, bug I do have a picture of my old knock sensors. The rear sensor was corroded as all hell, and the front one still looked basically new. There was about an inch of water in the cavity with the rear sensor that I had to suck out with a shop vac. I then blew it out with air to make SURE that it was dry before installing the new one.
I guess you can look at my picture and figure out which sensor was the rear sensor. [emoji38]

View attachment 64045

That's pretty wild. I swapped my engine at 165k and mine didn't look like that. They looked clean. Nothing in there.

 

[ScottyBoy]

That's pretty wild. I swapped my engine at 165k and mine didn't look like that. They looked clean. Nothing in there.

About 2 years ago I pressure washed my engine to clean it, because I was replacing the valve cover gaskets that were leaking oil down the heads. I bet that's how the water got in there. The knock sensor code started popping up about a year ago, and I would clear it then it would go away for a few weeks then pop up again. Then around 6 months ago it pretty much came right back on no matter how many times I reset it with my code reader. So this repair has be on my "to-do list" for about six months now, But it hasn't been a top priority because I don't drive my truck as much anymore since I'm unemployed. It sits in the driveway most of the time. But we had to take a road trip this week, and I did NOT want to be crammed in the damn Altima for six hours, so I went ahead and fixed everything on the Burban that needed to be fixed. I replaced the knock sensors, air filter, cleaned the throttle body, got two new tires, and replaced a window regulator all to prepare for this road trip.

 

[Danzigman]

The intake crimped the wire on the harness when I reinstalled the intake.

 

[pnwdan]

The intake crimped the wire on the harness when I reinstalled the intake.

Damn